Stem cells have shown great promise in treating a wide range of medical conditions. However, stem cell therapy often requires the administration of very large numbers of stem cells which are produced by the in vitro) expansion of tissue explants. Because stem cells are present in tissues in relatively small numbers, it is difficult to generate large numbers of stem cells for therapeutic use. This problem is complicated by the loss of differentiation potential that characterizes in vitro stem cell culture. As stem cells spend more time in culture and are encouraged to undergo multiple cell divisions, the differentiation potential of the stem cells diminishes (BMC Cell Biol. 2008 Oct. 28; 9:60; J Cell Physiol. 2005 November; 205(2):194-201). Thus, stem cells must be harvested after only a limited number of cell divisions in order to obtain stein cells having a desired level of differentiation potential.
What is needed in the art therefore is a method for expanding stem cells that extends the length of time that stem cells can remain in culture, permits the cells to undergo a greater number of divisions, and allows the stem cells to retain a desired level of stem cell differentiation and therapeutic potential.